| Chemical Abstract Number (CAS #) |
62737
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| Synonyms | Dichlorvos |
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Phosphoric acid, 2,2-dichlorovinyl dimethyl ester | DDVP | Vapona |
| Analytical Method |
EPA Method 8141A |
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| Molecular Formula | C4H7Cl2O4P |
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| Use | CHLORINATED ORGANIC PHOSPHATE INSECTICIDE WITH APPRECIABLE
VAPOR PRESSURE. INCORPORATED INTO PLASTIC STRIPS IT SLOWLY RELEASES
VAPOR. HAS BEEN APPROVED FOR USE IN DISINFECTION OF AIRCRAFT.
CONTACT & STOMACH INSECTICIDE WITH FUMIGANT & PENETRANT ACTION.
USED AS HOUSEHOLD & PUBLIC HEALTH FUMIGANT FOR PROTECTION OF
STORED PRODUCTS @ 0.5-1 G AI/100 CU M; FOR CROP PROTECTION AGAINST
SUCKING & CHEWING INSECTS @ 300-1000 G/HA.
ANTIHELMINTIC-EG, FOR SWINE, DOGS, & HORSES
Controls household, public health, stored product insects. Controls mushrooms, flies, aphids,
spider mites, caterpillers, thrips, white flies in glasshouse crops, outdoor fruit, vegetables.
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| Consumption Patterns | ESSENTIALLY 100% AS A PESTICIDE
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| Apparent Color | COLORLESS TO AMBER LIQUID
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| Odor | Mild chemical odor ; Aromatic odor
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| Boiling Point | 140 DEG C @ 20 MM HG
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| Molecular Weight | 220.98
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| Density | 1.415 @ 25 DEG C/4 DEG C
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| Sensitivity Data | Dichlorvos is not known to be an eye irritant.
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| Environmental Impact | Dichlorvos may be released to the environment during its production, disposal and use as
an insecticide in households and on crops and livestock. Dichlorovos is one of the more volatile
organophosphates. If released into water it will hydrolyze with a half-life of approximately 4 days
although its half-life varies considerably between pH 4 and 9. It will degrade very slowly at pH 4
and quite rapidly at pH 9. Biodegradation may aid in its disappearance, particularly when
acclimated colonies of microorganisms exist or under more acidic conditions when hydrolysis is
slower. Bioconcentration in fish will not be significant. The Henry's Law constant indicates that
volatilization of dichlorvos from environmental waters and moist soil should generally be slow.
The volatilization half-lives from a model river and a model pond, the latter considers the effects
of adsorption, have been estimated to be 57 and over 400 days, respectively. If released on land,
dichlorvos will leach into the ground water where it will hydrolyze and also degrade through
chemical and biological processes with reported half-lives ranging from 1.5-17 days. If released
into the atmosphere, dichlorvos is expected to exist almost entirely in the vapor phase in ambient
air. In air, vapor phase dichlorvos will react with photochemically generated hydroxyl radicals and
ozone with estimated half-lives of 2 and 320 days, respectivley. Human exposure will be primarily
from indoor air where dichlorvos is used as an insecticide and from food which has been prepared
where it is used.
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| Environmental Fate | TERRESTRIAL FATE: When spilled on soil, dichlorvos leached into the ground with
18-20% penetrating to 30 cm within 5 days of spraying in one experiment. It will degrade by both
hydrolysis and biodegradation. Half-lives of 7 days were obtained in clay, sandy-clay, and loose
sandy soil . A half-life of 1.5 days was obtained in field plots on chestnut soil and 17 days in
an unidentified soil . It disappeared from soil as well as foliage when sprayed on a vineyard in
the USSR . Dissipation rates on lawns were measured with and without postspray irrigation,
and it was not detected 24 hrs after application (detection limit 0.003 ug/sq cm) .
AQUATIC FATE: When released into water, dichlorvos will remain in the aqueous phase since it
will not adsorb appreciably to sediment. It will degrade primarily by hydrolysis although
biodegradation may be important where acclimated microorganisms may exist such as some
polluted waters or where the water is more acidic and hydrolysis slower. One investigator
reported 64% disappeared in 24 hr at pH 8.7 and only 8% at pH 6. Half-lives in lakes and rivers
are reported to be approximately 4 days . The Henry's Law constant indicates that volatilization
of dichlorvos from environmental waters should generally be slow . Based on the Henry's Law
constant, the volatilization half-life from a model river has been estimated to be 57 days(2,SRC).
The volatilization half-life from a model pond, which considers the effects of adsorption, has been
estimated to be over 400 days(3,SRC).
ATMOSPHERIC FATE: Based upon the vapor pressure, dichlorvos is expected to exist almost
entirely in the vapor phase in ambient air . In the atmosphere, vapor phase reaction with
photochemically produced hydroxyl radicals may be important fate processes. Vapor phase
reactions with ozone may also occur. The rate constant for the vapor-phase reaction of dichlorvos
with photochemically produced hydroxyl radicals has been estimated to be 9.24X10-11 cu
cm/molecule-sec at 25 deg C, which corresponds to an atmospheric half-life of about 2 days at an
atmospheric concentration of 5X10 5 hydroxyl radicals per cu cm . The rate constant for the
vapor-phase reaction of dichlorvos with ozone has been estimated to be 3.58X10-11 cu
cm/molecule-sec at 25 deg C which corresponds to an atmospheric half-live of about 320 days at
an atmospheric concentration of 7X10 11 molecules per cu cm . Dichlorvos will not directly
photolyze in the atmosphere.
Octanol water partition coefficients and air water partition coefficients were obtained for 10
organochlorine pesticides (including dichlorvos) as basic data for predicting their fate in the
environment. The octanol water partition coefficient is 1.45X10 1 for dichlorvos. These values
approximately correlated with the solubilities of these pesticides in water. The air water partition
coefficient is 5.0X10-3 for dichlorvos.
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| Drinking Water Impact | Dichlorvos has been detected in a water reservoir and water supply-irrigation system in
the USSR and in 4 polluted rivers . On September 9 to 11, 1988, dichlorvos was detected in
marine waters of Beirtreach Bay, Ireland at concentrations up to 0.13 ug/L .
EFFL: Dichlorvos was detected in wastewater from a dichlorvos production plant in Bulgaria 16
g/l .
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